Nhanh giúp mình với ạ

`a)2/(sqrt(3))`

`=(2.sqrt(3))/(sqrt(3).sqrt(3))`

`=(2sqrt(3))/3`

`b)(10-sqrt(5))/(9sqrt(5))`

`=((10-sqrt(5)).sqrt(5))/(9sqrt(5).sqrt(5))`

`=(10sqrt(5)-5)/45`

`=(5(2sqrt(5)-1))/45`

`=(2sqrt(5)-1)/9`

`c)(sqrt(2)-1)/(sqrt(2)+1)`

`=((sqrt(2)-1)(sqrt(2)-1))/((sqrt(2)+1)(sqrt(2)-1))`

`=((sqrt(2)-1)^2)/(2-1)`

`=(2-2sqrt(2)+1)/1`

`=3-2sqrt(2)`

`d)10/(sqrt(3)-5)`

`=(10(sqrt(3)+5))/((sqrt(3)-5)(sqrt(3)+5))`

`=(10(sqrt(3)+5))/(3-25)`

`=-(10(sqrt(3)+5))/22`

`=-(5sqrt(3)+25)/11`